The indicators should be applied to a curated, representative set
of
species -
100 to several thousand species per country, depending on a country’s
biodiversity, data capacity, and resources for CBD reporting.
Approximately 100 species is likely a minimum to represent diverse
habitats, taxonomic groups, commonness/ rarity, and threat status.
However, if 100 cannot be collected, any amount of data is important.
The two genetic diversity indicators are:
The first indicator is based on comparing the effective
population size of each population Ne to a critical threshold (e.g.
Ne = 500). For many species, it is sufficient and appropriate to use
the census size Nc (the number of living adults) as a proxy
for Ne, and a threshold of Nc = 5000 mature individuals. Below this
threshold, a population rapidly loses genetic diversity, can become
inbred, and starts to lose ability to adapt to environmental change.
The second indicator is based on comparing the current number
of populations that exist to a prior/ historic assessment of the
number of populations . This reflects loss of populations to
human-induced changes, with 50-200 years ago as a baseline (depending
on the country). If counts of populations existing and lost are not
available, a proportion (or percentage) of the species’ range are lost
is an acceptable substitute. Lastly, if this is not available, some
estimate of overall decline is acceptable (details will be explained
below).
The primary undertaking is to gather the data on populations for each
species. This is a challenge because there is no global, standard
database of population census size (The Living Planet Index for example
does not measure full population census, and not all Red List species
have census size for each population). But the census size of many
populations of many species is available in different reports and
databases, in more or less easy ways to extract. This guidance
document will explain how to gather and use the necessary data, from
diverse sources, in a standard way.
As noted above, a third indicator exists, which is to count the number
of genetic studies available for that species, if any. Although this
does not directly relate to maintenance of genetic diversity or
preventing genetic erosion, performing genetic studies and collecting
genetic data correlates to management actions designed to manage genetic
diversity- such studies help understand needed management actions and to
guide them. So we will also collect information on whether genetic
studies exist for species, for reporting on indicator 3. However, this
project will not use genetic datasets to calculate the Ne or Ncbecause reanalysis of data is time prohibitive- we are not downloading
and analyzing genetic data.
The Project Purpose This project was planned in 2021 and initiated in 2022 to test the
indicators in a small number of countries. The project goal is for each
country team to evaluate >100 species (per country) to
determine (a) how many species have the required data, (b) to extract
the data when possible for indicator calculation, and (c) to identify
barriers encountered so that this guidance document and indicator
calculation can be improved for larger scale use by more countries to
inform the CBD framework. The project will also highlight species and
regions where data is deficient, or where there is high uncertainty in
the estimates.